Computational and Experimental Evidence of Emergent Equilibrium Isotope Effects in Anion Receptor Complexes

Abstract

The measurement of a deuterium equilibrium isotope effect (EIE) for the aryl CH···Cl– interaction of anion receptor 1H/1D is reported. Computations corroborate the results of solution measurements for a small, normal EIE in the full complex (KaH/KaD = 1.019 ± 0.010). Interestingly, isotope effects involving fragments of the anion receptor (urea, aryl ring, etc.) are predicted to produce an inverse effect. This points to an unusual and subtle structural organization effect of the anion receptor complex that changes the nature of the combined interactions to a normal isotope effect. The reversal of EIE values suggests that overall architecture of the anion receptor can dramatically impact the nature of bonding in these complexes.

The road to aryl CH⋯anion binding was paved with good intentions: fundamental studies, host design, and historical perspectives in CH hydrogen bonding

“…13), and thus we embarked on a study with collaborator Paul Cheong's lab to investigate EIEs in an aryl CH HB an anion receptor. 51 In this investigation, receptors 21a H and 21a D were titrated with chloride in d 6 -DMSO and monitored through 13 C NMR titrations. We reported a normal DEIE, with K a 21 aH / K a 21 aD = 1.019 +/ − 0.010.…”

“…We reported a normal DEIE, with K a 21 aH / K a 21 aD = 1.019 +/ − 0.010. 51 We also reported the computed DEIEs of fragments of the receptors (Fig. 13).…”

Separation of halogenated benzenes enabled by investigation of halogen–π interactions with carbon materials

“…[1][2][3][4][5] This halogen bonding interaction has attracted interest in many elds, such as molecular biology 6,7 and crystal engineering, 8,9 due to its high molecular selectivity and linear directionality. [10][11][12][13][14] In particular, halogen bonding has been positively applied to develop new functional materials [15][16][17][18] since Nguyen et al rst synthesized liquid crystals designed with halogen bonds in 2004. 19 An example is the Rotaxane structure with iodo groups synthesized by Barendt et al that selectively recognized nitrogen anions via halogen bonding, producing drastic color changes.…”

Bumpy Roads Lead to Beautiful Places: The Twists and Turns in Developing a New Class of PN-Heterocycles

“…Towards this aim, our lab has developed several arylethynyl frameworks (Figure 1) capable of binding a variety of anionic guest molecules, including halides, [14][15][16][17][18] oxoanions, [19][20][21] and hydrochalcogenides. [22][23][24] These hosts take advantage of both their multidentate binding pockets formed from the meta-substitution of the phenyl or pyridyl cores with two arylethynyl arms as well as the fluorescent nature of the -conjugated backbone.…”

“…14 This opened a floodgate of 13 eventual co-advised students and postdocs over the next 14 years who explored anion--interactions, the effect of increasing or reducing the number of urea binding units, the effects of different heterocyclic cores, and the physical organic chemistry of these receptors and their guests. 16,[19][20][21][22][23][24] Along the way, graduate student Blake Tresca further improved upon the early designs by replacing the pH-sensitive pyridine core with a benzene as in 2 and showed that the C-H•••anion interaction could be tuned by installing electron-donating/electron-withdrawing groups para to the CH unit. 26 the National Academy of Inventors.…”